Stochastically Generated North American Megadroughts
Stochastically Generated North American Megadroughts
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DOI：
10.1175/jcli-d-13-00689.1
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发表时间：
2015-02
影响因子：
4.9
通讯作者：
S. Stevenson;A. Timmermann;Y. Chikamoto;Sally Langford;P. DiNezio
中科院分区：
文献类型：
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作者：
S. Stevenson;A. Timmermann;Y. Chikamoto;Sally Langford;P. DiNezio
通过使用 NCAR 社区地球系统模型 (CESM1.0.3) 的 T3133 分辨率版本进行的一系列模拟，研究了年际至十年间海面温度 (SST) 对美国干旱影响的重要性。该模型相当好地捕获了热带太平洋与北美降水的遥相关，尽管地形特征在更高分辨率下有所增强。通过比较两个理想化的 1000 年 CESM1.0.3 实验来分离海温异常的贡献：完全耦合控制和仅大气 (CAM4) 运行，强制使用来自控制的海温气候学。干旱使用帕尔默干旱严重指数 (PDSI) 进行识别，该指数是根据 CESM1.0.3 实验在美国四个地区计算得出的，并与北美干旱进行比较 Atlas(NADA).The CESM1.0.3reproduces the persistence of NADA droughtsquitewell, although the model underestimates drought severity.在CESM1.0.3框架内，海温强迫不会显着影响干旱强度或发生频率，即使是持续时间长达15年或更长的“特大干旱”。在CESM1.0.3和NADA中，除美国东南部外，所有地区的干旱强度、持续时间和发生频率在统计上均与红噪声原假设一致。这意味着海温强迫并不是造成干旱的主要因素，因此许多十年间的特大干旱是由内部大气变化和与陆地表面的耦合共同引起的，而海温异常仅发挥次要作用。
The importance of interannual-to-decadal sea surface temperature (SST) influences on drought in the United States is examined using a suite of simulations conducted with the T3133 resolution version of the NCAR Community Earth System Model (CESM1.0.3). The model captures tropical Pacific teleconnections to North American precipitation reasonably well, although orographic features are somewhat enhanced at higher resolution. The contribution of SST anomalies is isolated by comparing two idealized, 1000-yr CESM1.0.3 experiments: a fully coupled control and an atmosphere-only (CAM4) run forced with the SST climatologyfromthecontrol.Droughtsareidentified usingthePalmerDroughtSeverityIndex(PDSI),which is computedoverfour U.S. regionsfrom the CESM1.0.3experiments and comparedwiththe North American Drought Atlas(NADA).The CESM1.0.3reproduces the persistence of NADA droughtsquitewell, although the model underestimates drought severity. Within the CESM1.0.3 framework, SST forcing does not significantly affect drought intensity or frequency of occurrence, even for very persistent ‘‘megadroughts’’ of 15yr or more in length. In both the CESM1.0.3 and NADA, with the exception of the Southeast United States, droughts in all regions have intensities, persistence lengths, and occurrence frequencies statistically consistent with a red noise null hypothesis. This implies that SST forcing is not the dominant factor in generating drought and therefore that many decadal megadroughts are caused by a combination of internal atmospheric variability and coupling with the land surface, with SST anomalies playing only a secondary role.